Certain clinical and necropsy findings are described in 13 patients who had both aortic dissection (AD) and fusiform abdominal aortic aneurysm (AAA). All 13 patients had severe and extensive aortic atherosclerosis. The AAA was diagnosed clinically in 9 patients and 5 had the AAA resected. The AD was diagnosed clinically in 5 patients and 2 underwent attempted operative repair. Two patients who had the AAA resected because of suspected rupture later were found to have ruptured a more proximal AD. Thus, AD occurs occasionally in patients who have AAA. In older persons with suspected rupture of an AAA, a more proximal rupture of an AD should be ruled out. When both AAA and AD are present in the same patient, the AD more likely is the cause of cardiovascular collapse than is rupture of the AAA.